Date of Award
M.S. in Engineering Science
Water scarcity and the emergence of new contaminants are making the world in need of renewable water resources. Slow sand filtration is looked at as an affordable and easy method to filter water with a few weaknesses such as clogging and the inability to remove complex matrix ingredients. To overcompensate these limited weaknesses, graphene-coated sand was studied. Ottawa, concrete, and masonry sand were used, using a reduction method to transform a coating of sugar into elemental carbon in N2 atmosphere at temperatures reaching 750°C. After that, the synthesized materials were activated using sulfuric acid. To verify the effectiveness of the coating process used, a digital microscope, Raman spectroscopy, scanning electron microscope, and energy-dispersive X-ray spectroscopy were implemented. After that, flow-through columns were used to evaluate the ability of the different materials to remove turbidity and bacteria. Due to the additional expense related to the activation process, columns packed with graphene sands were tested alongside the non-activated ones as well as columns containing the raw sands.
The digital microscope revealed that rounded (Ottawa sand) particles were coated less efficiently than sub-angular and angular particles (concrete, and masonry sand). The Raman spectroscopy revealed the formation of G and D bands in all graphitized sands suggesting complete graphitization of the sugar and the presence of defect site necessary for the adsorption of contaminants. Furthermore, the peak intensity was 30% higher in concrete and masonry graphitized sands compared to Ottawa graphitized sand solidifying the visual characterization. SEM on the samples revealed the formation of carbon sheets 10 nm thick and EDS results backed up the geological identification of the sands with quantification of the elements.
The graphene-coated sand dominated the turbidity stress test. The graphene-coated Ottawa (GCOS) sand lasted high turbidity by more than 15% longer when compared to raw Ottawa sand (ROS). And the effluent turbidity value was 25% lower in GCOS compared to ROS.
Bacteria removal in both Ottawa and masonry sand increased with graphene coating, concrete sand maintained removal higher than 90% when coated. The difference in effectiveness of the activation is minuscule and cannot be justified with the current work.
Nusair, Abdulla, "GRAPHENE SAND COMPOSITES AND THEIR APPLICATIONS IN WATER TREATMENT" (2021). Electronic Theses and Dissertations. 2167.